When an order downloads from eBay, Brightpearl will apply tax rules to work out which tax code should be assigned to the order and therefore what the tax amount is.
Making the tax rules work for you
If you are a UK based seller and make a sale to a UK based customer, the tax code is usually driven by the product. So to ensure this is the case, do not assign any tax code to your United Kingdom tax zone, but ensure your products are assigned the relevant tax code.
If you are a UK based seller and make a sale to a customer outside of the UK, then the tax code will usually be driven by the location of the customer. So to ensure this is the case, assign the relevant tax code to your tax zones at Settings > Localization > Tax Zones .